Differential pressure regulator

ABSTRACT

An improved differential pressure regulator having two continuous, hole-free diaphragms provided with a solid plug which is located between the diaphragms and is capable of moving with the movement of the diaphragms.

United States Patent 1191 Maercklein I 1 Oct. 2, 1973 1541 m F 'n LPRESSURE REGULATOR 3,432,152 3 1969 swt-cnt- 25l/6l.4 x

, 1,539,630 5/1925 BCfliId 1 251 61.3 x

{75] Inventor: Charles D. Maercklein, Milwaukee, 294L546 6/1960 C0whcrdH 25% x 3,446,241 5 1969 sk61i 25l/61.4 x

. 3,463,442 8/1969 Leskicwicz ct al. 1. 25l/6l.2

[73] Assgnee' Isotopes weslwood' 2,329,323 9 1943 Benz 137 505.13 x [22]Filed: Apr. 30, 1971 Appl. No.: 139,162

11.8. Cl. 137/98, 251/613 Int. Cl 60511 11/02, F16k 31/45 Field ofSearch 251/613, 61, 61.2, 251/367, 61.4; 137/505.13, 505.39, 509, 312,505.42, 510, 494, 98

References Cited UNITED STATES PATENTS Mangiameli 137/98 PrimaryExaminerArn01d Rosenthal AtlorneyFleit, Gipple and Jacobson [57]ABSTRACT An improved differential pressure regulator having twocontinuous, hole-free diaphragms provided with a solid plug which islocated between the diaphragms and is capable of moving with themovement of the diaphragms.

9 Claims, 6 Drawing Figures PATENTEUBBT 2W5 3.762.430

SHEET 1 OF 2 "lll lll'lf l7 1 DIFFERENTIAL PRESSURE REGULATOR BACKGROUNDOF THE INVENTION This invention relates to differential pressureregulators and a specific improvement therein.

Differential pressure regulators are well known devices and are used tocontrol the pressure of one gas stream, or the contolled gas stream byreference to the pressure of a second gas or the reference gas" stream.

A typical differential pressure regulator is composed of a number ofadjoining chambers, the chambers being separated by a movable diaphragm.One of the chambers is connected to the reference gas line so thepressure in that chamber is the same as the pressure in the referencegas stream.

A second gas chamber adjoins the first gas chamber so that the diaphragmdefining one side of the first gas chamber also defines a side of thesecond gas chamber. The regulator is constructed so that the gas to becontrolled enters the second chamber through an inlet opening and leavesthe chamber through an exit opening. Also, a valve which controls theflow of gas through the second chamber is attached in some way to thediaphragm so that it opens and closes in response to the movement of thediaphragm.

A valve generally used in the typical differential pressure regulator isa needle valve which comprises a conical member positioned so that itcan move into and out of contact with an orifice thereby controlling theflow of gas through the orifice.

In operation, the position of the valve is determined by the relativeforces provided by the pressure of the reference gas on one side of thediaphragm and the pressure of the control gas on the other side of thediaphragm. The valve which is connected to the diaphragm is so arrangedthat a change in pressure in the reference gas causes the diaphragm tomove one way or the other. This in turn activates the valve to open orclose thereby decreasing or increasing the flowrate of the controlledgas out of the second chamber. This causes a corresponding change in thepressure of the second chamber so that the pressure in the secondchamber increases if the pressure in the first chamber increases andvice versa. This change in pressure brings the diaphragm back to itsoriginal position and thus the system comes back to equilibrium.

Such a device can be made so that a low pressure gas can control a highpressure gas. This is done by inserting a spring in the first chamberbiasing the diaphragm to causethe valve in the second chamber to remainopen. Thus, in order for the diaphragm to be in equilibrium, the forceexerted by the high pressure gas in the second chamber must overcome notonly the force produced by the pressure of the low pressure gas in thefirst chamber but also the force of the biasing spring.

In another modification of this basic regulator, two diaphragms areprovided, and a space is maintained between them. This modification isused in situations where the reference gas and the controlled gas formpotentially explosive mixtures. The space between the diaphragms isusually vented to the atmosphere, so that if some gas from one chamberleaks into the space between diaphragms, it is vented to the atmosphere.In this modification, the two diaphragms are connected by a solid linkwhich usually extends through the center of each diaphragm and isconnected to the diaphragm by a system of washers spaced on each side ofeach diaphragm. This is done to maintain a constant distance between thetwo diaphragms, so that movement of one diaphragm will be communicatedto the other diaphragm.

These differential pressure regulators suffer from certain drawbackswhich render them unsuitable for certain applications. In particular,the differential pressure regulators of the prior art have not beenfound to work entirely successfully when used in commercially feasiblewater electrolysis processes. In such processes two electrodes areusually placed in a container of an electrolyte and an asbestos sheet,separated from each electrode by a nickel screen, is provided for thesite of the electrolysis reaction. When an electric current is suppliedto the electrodes, hydrogen is given off on one side of the asbestossheet and oxygen is given off on the other side of the asbestos sheet.In this process, it is essential to keep the pressure of the oxygenproduct stream a given amount, for example, 10 psi, below the pressureof the hydrogen product stream. Moreover, it is essential to keep thispressure differential relatively constant, for example, within plus orminus four psi regardless of the pressure of the system. In particular,it is necessary to keep this pressure differential relatively constantbeginning with the initial start-up of the process, when both thehydrogen and the oxygen pressures are zero. The differential pressureregulators known in the prior art are incapable of providing this resultin a safe and efficient manner.

A single diaphragm differential pressure regulator is unsatisfactory,because the potentially reactive hydrogen and oxygen are notsufficiently segregated from each other. Because the diaphragm in thisregulator is usually connected to the control valve by a system ofwashers and links extending through the diaphragm, the hydrogen andoxygen can easily leak through the diaphragm. It has been found that asingle diaphragm regulator can be used for only a relatively short time,such as a day or two, before either hydrogen or oxygen leaks into theother chamber and causes an explosion inside the regulator.

While a double diaphragm differential pressure regulator alleviates thisproblem somewhat, it still is not entirely satisfactory. Even thoughmost of the gas that leaks through either of the diaphragms in this typeregulator is vented to the atmosphere, some gas remains. This residualgas together with the gas which leaks from the other diaphragm issufficient to cause internal explosions in this type of regulator aftera few days use.

In addition to the above, none of the differential pressure regulatorsof the prior art has been able to both effectively control the pressureof a low pressure gas stream by reference to a high pressure gas and atthe same time provide a reasonably constant pressure differential fromzero pressure up to the ultimate operating pressures.

The basic single diaphragm regulator cannot provide a pressuredifferential at all. Moreover, even when containing a biasing means suchas a spring to provide a pressure differential, this type of regulatoris only used to control a high pressure gas with a low pressure gas. Thetypical double diaphragm regulator also controls a high pressure gaswith a low pressure gas.

A few attempts have been made to control a low pressure gas with a highpressure gas by employing a double diaphragm regulator having differentsize diaphragms, but these devices are incapable of providing areasonable pressure differential at low pressures.

In addition, the dependability of the typical differential pressureregulator decreases with time, because the generally used needle valvedevelops significant leaks after a relatively short period of time.

It is an object of this invention to provide a differential pressureregulator which can be safely used with gases that form a potentiallyexplosive mixture.

It is another object of this invention to provide a differentialpressure regulator which can effectively control a low pressure gasstream by reference to a high pressure gas.

It is a still further object of this invention to provide a differentialpressure regulator which can control a low pressure gas by means of ahigh pressure gas and at the same time provide a reasonably constantpressure differential from zero pressure to a reasonably high pressure.

It is a still further object of this invention to provide a differentialpressure regulator in which the controlled gas line does not developsignificant leaks after a short period of time.

Brief Summary of the Invention These and other objects are accomplishedaccording to this invention whereby a differential pressure regulatorhaving two continuous diaphragms separated by a solid plug is provided.Moreover, in a particularly preferred embodiment of this invention, ameans biasing the valve controlling the flow of the controlled gasthrough the regulator in an open position is also provided.

BRIEF DESCRIPTION OF THE DRAWINGS The nature of this invention can bebetter understood by reference to the following drawings wherein FIG. 1is an exploded axial section view of the improved differential pressureregulator of this invention showing how the parts are assembled.

FIG. 2 is a side view of the plug used according to this invention.

FIG. 3 is a side view of the spacer used according to this invention.

FIG. 4 is an enlarged view of part of the improved differential pressureregulator shown in FIG. 1.

FIG. 5 is a top view of a diaphragm used in the improved differentialpressure regulator of this invention, and

FIG. 6 is an axial section view of the improved differential pressureregulator of this invention when assembled.

DETAILED DESCRIPTION Referring specifically to FIG. 1, the improveddifferential pressure regulator of this invention is preferably circularin cross-section and comprises a bonnet 11 located in the upper portionof the regulator and a base 10 located in the lower portion of theregulator. The bonnet 11 is provided with an inlet 5 for the referencegas. The base 10 is provided with an inlet 6 which is in fluidcommunication with a cavity 22 by means of channel 24. Cavity 22 is alsoin fluid communication with exit port 7 by means of channels 26 and 27.A cylindrical seat 14, 14K is provided around channel 26 in order toreceive a spring 15. The seat l4, l4 and the channel 26 define acylindrical extension 32, 32' having end faces 34, 34'.

A valve generally indicated at 85, is composed as follows. An O-ring 12having a radius substantially the same as the radius of extension 32,32' is located above face 34, 34' of extension 32, 32. Located directlyabove O-ring l2 and channel 26 in base 10 is a needle 13 having inclinedsurface 38, 38' and top portion 52 with flange 65, 65'. The O-ring l2and needle 13 are located so that downward movement of the needle 13will cause inclined surface 38, 38' to abut O-ring 12 which in turnabuts end face 34, 34' of extension 32, 32' to thereby close valve 85.This cuts off the flow of any gas flowing from cavity 22 to channel 26.The use of an O-ring and needle in this manner prevents any gas leakingfrom cavity 22 to chamber 26 when valve is closed.

The closing of valve 85 is caused by means of the unique doublediaphragm system of this invention. This system comprises diaphragms 3and 4 and plug 1 and spacer 2, which are located between diaphragms 3 4.Plug l is a solid piece of material having end faces 41 and 42 and aflange 43, 43' extending radially outward from the center of the plugbetween faces 41 and 42.

Spacer 2 is a solid piece of material containing two cylindrical holesgenerally indicated at 48 and 49 concentric with spacer 2. The radius ofhole 48 is slightly larger than the radius of end face 41 of plug 1, andthe radius of hole 49 is slightly larger than the radius of flange 43,43 of plug 1. This enables plug 1 to fit generally inside of spacer 2with the portion of plug I extending above the top of flange 43, 43' anddefined by face 41 fitting within hole 48 of spacer 2 and the portion ofplug 1 extending below the top of flange 43, 43' fitting into hole 49 ofspacer 2. Moreover, plug 1 is further constructed so that it is able toslidably move from this position away from inside spacer 2 towards base10. In addition, spacer 2 is provided with vents 8 and 9 which allowhole 49 to communicate with the outside atmosphere. These vents areprovided so that any gas which inadvertently passes through either ofthe diaphragms may be vented to the atmosphere. In particular, vents 8and 9 are in fluid communication with the faces of diaphragms 3 and 4abutting plug 1, regardless of the position of plug 1, because ofconstruction tolerances necessary to allow plug 1 to slidably move inspacer 2.

Located between diaphragm 4 and needle 13 is washer 17. This washer isprovided with recess 51 which is capable of engaging the top portion 52of needle 13 allowing washer 17 to center needle .13 for engagement withO-ring 12 and face 34, 34' of extension 32, 32' of base 10. Moreover,washer 17 allows the contact between needle 13 and diaphragm 4 to be aslarge as possible, thereby minimizing the dangers of puncturing orotherwise destroying diaphragm 4 through excess wear of the diaphragm ina very localized area.

As can be seen from FIG. 5, the diaphragms used according to thisinvention are continuous sheets or films of material and contain noholes on their active surfaces, that is the surfaces of the diaphragmseffected by the gas pressure, to receiveconnecting shafts or cylinders.Moreover, in the operation of the improved differential pressureregulator of this invention, the diaphragms are free to travel inresponse to pressure variations and are not connected in their activeservices to anything. Remarkably, this specific designed featureprevents the leakage of both the reference gas and the controlled gasinto the space between the double diaphragms, which enables the improveddifferential pressure regulator of this invention to be safely used withpotentially explosive combinations of gases.

In addition, the use of vents 8 and 9 provides an additional safetyfactor in that if one of the diaphragms becomes damaged and allows gasto leak between the double diaphragms, an explosion is prevented becausethis gas will be vented to the atmosphere.

The diaphragms of this invention can be made from any material flexibleenough to repeatedly move in operation and yet stable against thecorrosive gases and contaminant liquids present in the gas streams. Inaddition, each diaphragm may be constructed of more than one layer ofmaterial in order to provide a diaphragm with properties not obtainablefrom a single layer diaphragm. For example, a diaphragm which has beenfound to be particularly useful is one made from a layer of Teflon nextto a layer of rubber. The exact materials used to make the diaphragms ofthis invention are all well known in the art, and the selection of thesematerials forms no part of this invention.

When the parts of the improved differential pressure regulator of thisinvention are assembled together, ring 12 rests against face 34, 34. ofextension 32, 32' of base 10. Spring 15 abuts against the lower face offlange 65, 65 of needle 13 and thus biases needle 13 away from channel26. Washer 17 abuts against needle 13 so that top portion 52 of needle13 is located in recess 51 of washer l7. Washer 17 rests against the lowsurface of diaphragm 4, and through the force provided by spring 15,pushes plug 1 inside spacer 2 so that the lower face of spacer 2 isgenerally flush with face 42 of plug 1 and the upper face of spacer 2 isgenerally flush with face 41 of plug 1. Diaphragm 3 rests against therelatively flat surface formed by the upper face of spacer 2 and face 41of plug 1. The bonnet 11 then rests against the outside top surface ofdiaphragm 3.

The various parts of the improved differential pressure regulator ofthis invention are held together by conventional means. The nature ofthis means is not critical, and its design is evident to one of ordinaryskill in the art. For example, the parts can be held together by aseries of bolts extending from flange 63, 63' of bonnet 11 throughdiaphragm 3, spacer 2, diaphragm 4 and base 10 when they are securedwith a series of nuts. Alternatively, C-clamps extending from flange 63,63' of bonnet 11 to the bottom of base 10 can be provided to compressthe parts together.

The various parts of the improved differential pressure regulator ofthis invention, aside from the diaphragms, can be made from anymaterials which do not corrode when in contact with the gases used orthe contaminant liquids in the gases. For example, it has been foundthat stainless steel works very well in a great variety of applications.The proper selection of materials can be easily accomplished by theskilled artisan and forms no part of this invention.

In the operation of the improved differential pressure regulator of thisinvention, a line containing the reference gas is connected to inlet 5of bonnet 11. A line containing the gas to be regulated, the controlledgas, is connected to inlet 6 of base 10 so that the controlled gas canflow through base 10 out exit port 7. The static pressure of thereference gas in cavity 95 formed by bonnet 11 and diaphragm 3 causes aforce to be exerted by diaphragm 3 against face 41 of plug 1. Thisforce, of course, depends on the surface area of face 41 and thepressure in cavity 95. When the plug 1 is in equilibrium and needle 13is located, for example, in the middle of its path of travel, this forceis exactly balanced by an opposing force comprising the force of spring15 and the force due to the pressure of the controlled gas in cavity 22of base 10 against diaphragm 4. If the reference gas pressure increases,plug 1 is forced downward, which in turn forces needle 13 closer to O-ring 12 and end face 34, 34 of extension 32, 32'. Since this narrows theopening in valve 85, the flow-rate of gas through base 10 is reduced,thereby increasing the upstream pressure of that gas. Thus, as can beseen an increase in the pressure of the reference gas causes acorresponding increase in the pressure of the controlled gas.

Alternatively, if the pressure of the reference gas decreases the forceexerted against plug 1 by diaphragm 3 decreases allowing the forceprovided by spring 15 and the pressure of the controlled gas in cavity22 of base 10 against diaphragm 4 to push plug 1 further into spacer 2.This in turn increases the distance between needle 13 and face 34, 34'of extension 32, 32', which increases the flow-rate of the controlledgas through base 10, thereby lowering the upstream pressure of thecontrolled gas.

Also, the improved differential pressure regulator of this invention iscapable of automatically maintaining the desired pressure differentialregardless of upstream changes in the flow-rate of the controlled gas.This is so because an upstream increase or decrease in the flow-rate ofthe controlled gas causes a corresponding increase or decrease in thepressure in cavity 22. This in turn causes valve 85 to open or close,thereby increasing or decreasing the flow-rate of the controlled gasthrough valve 85, which brings the pressure in cavity 22 back to itsoriginal value.

As can be seen from FIGS. 1, 2, and 3, the plug 1 and spacer 2 arepreferably built so that faces 41 and 42 of plug 1 have different areas.In the embodiment shown in these figures, the area of face 41 is smallerthan the area of face 42. This enables the improved differentialpressure regulator of this invention to control the pressure of a lowpressure gas with a high pressure gas. This is very desirable in certainapplications and in particular in a water electrolysis process, aspreviously referred to, where the oxygen pressure must be maintained ata constant amount below the hydrogen pressure.

Moreover, by the use of a plug having faces with different areas, notonly is it possible to control a low pressure gas with a high pressuregas, but is is also possible to selectively control the pressuredifferential provided by the regulator. This is so because the forceprovided by each diaphragm is a function of the area of the adjacentface of the plug 1 as well as the pressure against that diaphragm. Thusthe area of a first face of plug 1 can be increased or decreased withrespect to the area of the secondface without changing the ultimateforce provided by the first diaphragm, so long as the pressure againstthat diaphragm is correspondingly decreased or increased. Thus bychanging the ratio of the areas of the plug faces the pressuredifferential necessary to bring the plug to equilibrium can be varied.

In addition to the above design, the plug 1 and spacer 2 can be made sothat the area of face 41 is the same as the area of face 42. In thissituation, the regulator can maintain the pressure of a controlled gasstream to substantially the same pressure as the reference gas.Moreover, by appropriate selection of spring 15 in this situation, theregulator is capable of providing a relatively constant pressuredifferential between a high pressure reference gas and a low pressurecontrolled gas.

in particular, if the areas of faces 41 and 42 are the same, theimproved differential pressure regulator of this invention can maintaina relatively constant pressure differential regardless of the pressureof operation. This is so because the net force acting on plug 1 from thetwo gases is the product of the common area of the plug faces and thenet pressure difference between the reference gas and the controlledgas.

This relationship, however, does not hold true for the improved pressuredifferential regulator when the areas of faces 41 and 42 are different.in this situation, the pressure differential provided by the regulatordoes not vary directly with a change in operating pressures. This is sobecause as the pressures of the system increase, the force provided bythe diaphragm adjacent the larger face of plug 1 increases at a fasterrate than the force provided by the other diaphragm. The reason for thisis that the force provided by each diaphragm on plug 1 is a function ofnot only the pressure against the diaphragm but also the area of thediaphragm.

A unique advantage of the improved differential pressure regulator ofthis invention is that even though it employs a plug whose faces havedifferent areas, and is thus able to control a low pressure gas by ahigh pressure gas, it is still able to provide a relatively constantpressure differential between the high pressure reference gas and thelow pressure controlled gas over a relatively broad range of operatingpressures. This unique advantage is inherent in the design of theimproved differential pressure regulator of this invention and isparticularly due to the spring 15 shown in FIGS. 1 and 4. By the use ofthis spring, it is possible to provide a relatively constant pressuredifferential from an operating pressure of as low as zero psig. to anyoperating pressure desired. This is particularly useful in the waterelectrolysis process referred to above, where a relatively constantpressure differential must be maintained between the high pressurehydrogen stream and the low pressure oxygen stream from the moment thereaction begins at zero psig. to the final operating pressure.

Starting from an initial pressure of zero psig. in both streams to theultimate operating pressure, the improved differential regulator of theinvention provides a relatively constant pressure differential in thefollowing manner. At start up, spring 15 biases needle 13 in itsuppermost position, since at zero reference gas pressure there is noforce exerted on plug 1 by diaphragm 3. As gas begins to flow intopressure inlet tube in bonnet 1], pressure in cavity 95 increases,thereby causing diaphragm 3 to exert a force on plug 1. However, sincespring 15 is pushing against needle 13, causing diaphragm 4 to pushagainst plug 1, the increase in pressure in cavity 95 is not sufficientto close valve 85 until the force provided by diaphragm 3 against face41 slightly exceeds the force provided by spring 15. Thus, until thepressure in cavity 95 builds to a predetermined value, which as can beseen depends on spring 15, valve 85 remains open and the controlled gascontinues to flow through base 10. Of course, as soon as valve closes,the increase in pressure of the controlled gas in cavity 22 acts ondiaphragm 4 to force the valve 85 slighly open. In effect, valve 85comes to equilibrium so that the force provided by diaphragm 3 is equaland opposite to the sum of the force provided by spring 15 and the forceprovided by diaphragm 4.

As the pressures in the system approach the predetermined operatingpressures the relative effect of spring 15 becomes less and lesscompared to the forces provided by diaphragms 3 and 4. This is sobecause the force provided by the spring 15 is constant, while theforces provided by the diaphragms 3 and 4 vary directly with thepressures in cavities and 22 respectively.

Moreover, as the pressures of the system increase, the pressuredifferential provided between the reference gas and the controlled gasincreases. This is so because the faces 41 and 42 in plug 1 havedifferent areas. As a result, an increase in pressure in cavity 95requires a correspondingly smaller increase in pressure in cavity 22 tokeep the plug 1 in equilibrium, since the opposing forces provided bydiaphragms 3 and 4 are functions not only of the pressures of thecavities 95 and 22 but also of the areas of faces 41 and 42.Furthermore, this effect becomes more pronounced when the ratio of theareas of faces 41 and 42 increases.

Thus as can be seen, the pressure differentials provided by theregulator anywhere between zero pressure and the ultimate operatingpressures are a function of the size of spring 15 and the areas of plugfaces 41 and 42. Moreover, the rate at which the pressure differentialincreases with increasing pressure is a function of the ratio of theareas of the plug faces. Thus, by appropriate selection of theseparameters, an improved differential pressure regulator having thedesired operating characteristics can be made.

In order to select the proper plug face sizes and spring size for aknown ultimate operating reference gas pressure, a desired ultimatepressure differential and a desired initial pressure differential, thefollowing steps can be followed: First, the area of face 41 is selected.Next, since the initial pressure drop, and hence the initial pressure incavity 95 when valve 85 first closes is known, the force exerted bydiaphragm 3 on plug 1 can be calculated. In particular, at the instantvalve 85 closes, this force is approximately equal to the force providedby spring 15. Thus spring 15 can be chosen accordingly. it is preferableto select spring 15 so that its force remains relatively constant fromits maximum extended position to its maximum contracted position in theregulator.

The area of face 42 cannot be directly calculated, since the position ofneedle 13 and hence the force exerted by spring 15 are not known whenthe regulator is operating at its ultimate operating pressure. Ratherthe area of face 42 can be obtained by trial and error. A very goodguide can be made, however, by assuming the spring force at the ultimateoperating conditions is the same as the spring force of the spring whenit is fully compacted. Since spring 15 has been selected so that itsforce remains relatively constant regardless of its displacement, thisassumption is relatively accurate. The area of force 42 can then becalculated by assuming that the plug 1 is in equilibrium.

In another preferred embodiment, bonnet 11 can be provided with a springand means to vary the compressive force of this spring. The spring ispositioned inside cavity 95 so that it exerts a force biasing diaphragm3 against plug 1. This spring provides a force which is exactly oppositeto the force provided by spring 15. Thus, because the spring in chamber95 is variable, the ultimate force provided by the two springs, andhence the ultimate effect provided by spring 15 can be easilycontrolled. This enables the response of the regulator to be finelytuned to provide the exact operating characteristics desired.

While the above invention has been specifically described with referenceto controlling a low pressure gas by reference to a high pressure gas,the regulator can be used in any application where differential pressureregulators of the prior art have been used.

I claim:

1. A differential pressure regulator for maintaining the pressure of acontrolled gas upstream of the regulator a predetermined and constantamount above the pressure of a reference gas, said regulator comprising:a first continuous diaphragm; a chamber adjacent said first diaphragmand formed on one side by said first diaphragm, said chamber includingmeans for receiving said reference gas; a second continuous diaphragmgenerally parallel to and spaced from said first diaphragm apredetermined distance; plug means intermediate said first and seconddiaphragms, said plug means having a first substantially fiat face incontact with said first diaphragm and a second substantially flat facein contact with said second diaphragm, the width of said plug meansbetween said first and second faces being substantially the same as saidpredetermined distance; a valve in contact with said second diaphragm,said valve adapted to open and close in response to movement of saidsecond diaphragm; a second chamber adjacent said second diaphragm andformed in part by said second diaphragm, said second chamber beingadapted to receive said controlled gas; biasing means in said secondchamber for exerting a force on said plug means tending to move saidplug means towards said first chamber thereby opening said valve means;inlet means for passing controlled gas into said second chamber; andexit means for passing controlled gas through said valve means and outof said second chamher; said apparatus further characterized in that thecross sectional area of said first face is smaller than the crosssectional area of said second face.

2. Apparatus according to claim 1 wherein said biasing means is adaptedto exert a substantially constant force from its maximum extendedoperating position to its minimum contracted operating position.

3. Apparatus according to claim 1 further including spacer meansintermediate said first and second diaphragm, said spacer means havingan aperture therein for receiving said plug means, said aperture havinga smaller cross sectional area on the side of said spacer means facingsaid first diaphragm than on the side of said spacer means facing saidsecond diaphragm.

4. Apparatus according to claim 3 wherein the cross sectional area ofthe side of the plug facing said first diaphragm is smaller than thecross sectional area of the aperture in said spacer means facing saidfirst diaphragm and further wherein the cross sectional area of the sideof said plug facing said second diaphragm is smaller than the crosssectional area of the side of said spacer means facing said seconddiaphragm.

5. Apparatus according to claim 4 wherein the cross sectional area ofsaid plug means in an area intermediate its faces is substantially thesame as the cross sectional area of the aperture on the side of saidspacer means facing said second diaphragm.

6. Apparatus according to claim 1 wherein said valve comprises acircular aperture through which controlled gas is adapted to flow, aneedle having tapered sides adapted to move into and away from saidcircular aperture, and an O-ring having a diameter substantially thesame as the diameter of said circular aperture, said O- ring coaxiallymounted on said circular aperture.

7. Apparatus according to claim 6 wherein said biasing means acts onsaid needle.

8. Apparatus according to claim 7 wherein said biasing means is aspring.

9. Apparatus according to claim 1 wherein said biasing means is aspring.

1. A differential pressure regulator for maintaining the pressure of acontrolled gas upstream of the regulator a predetermined and constantamount above the pressure of a reference gas, said regulator comprising:a first continuous diaphragm; a chamber adjacent said first diaphragmand formed on one side by said first diaphragm, said chamber includingmeans for receiving said reference gas; a second continuous diaphragmgenerally parallel to and spaced from said first diaphragm apredetermined distance; plug means intermediate said first and seconddiaphragms, said plug means having a first substantially flat face incontact with said first diaphragm and a second substantially flat facein contact with said second diaphragm, the width of said plug meansbetween said first and second faces being substantially the same as saidpredetermined distance; a valve in contact with said second diaphragm,said valve adapted to open and close in response to movement of saidsecond diaphragm; a second chamber adjacent said second diaphragm andformed in part by said second diaphragm, said second chamber beingadapted to receive said controlled gas; biasing means in said secondchamber for exerting a force on said plug means tending to move saidplug means towards said first chamber thereby opening said valve means;inlet means for passing controlled gas into said second chamber; andexit means for passing controlled gas through said valve means and outof said second chamber; said apparatus further characterized in that thecross sectional area of said first face is smaller than the crosssectional area of said second face.
 2. Apparatus according to claim 1wherein said biasing means is adapted to exert a substantially constantforce from its maximum extended operating position to its minimumcontracted operating position.
 3. Apparatus according to claim 1 furtherincluding spacer means intermediate said first and second diaphragm,said spacer means having an aperture therein for receiving said plugmeans, said aperture having a smaller cross sectional area on the sideof said spacer means facing said first diaphragm than on the side ofsaid spacer means facing said second diaphragm.
 4. Apparatus accordingto claim 3 wherein the cross sectional area of the side of the plugfacing said first diaphragm is smaller than the cross sectional area ofthe aperture in said spacer means facing said first diaphragm andfurther wherein the cross sectional area of the side of said plug facingsaid second diaphraGm is smaller than the cross sectional area of theside of said spacer means facing said second diaphragm.
 5. Apparatusaccording to claim 4 wherein the cross sectional area of said plug meansin an area intermediate its faces is substantially the same as the crosssectional area of the aperture on the side of said spacer means facingsaid second diaphragm.
 6. Apparatus according to claim 1 wherein saidvalve comprises a circular aperture through which controlled gas isadapted to flow, a needle having tapered sides adapted to move into andaway from said circular aperture, and an O-ring having a diametersubstantially the same as the diameter of said circular aperture, saidO-ring coaxially mounted on said circular aperture.
 7. Apparatusaccording to claim 6 wherein said biasing means acts on said needle. 8.Apparatus according to claim 7 wherein said biasing means is a spring.9. Apparatus according to claim 1 wherein said biasing means is aspring.